PROJECTION OPTICAL SYSTEM, AND HEAD-UP DISPLAY DEVICE

It is an object of the present invention to provide a projection optical system having a minimal optical configuration while ensuring necessary capabilities and a head-up display device having a tilted virtual image plane. The head-up display device according to the present invention includes an image forming unit to emit image light containing image information and an eyepiece optical system to display a virtual image by reflecting the image light. While a virtual image plane is tilted to display a virtual image in a range from a far distance to a near distance, a point on the image forming unit conjugating to a far point on the virtual image plane is optically farther from a light flux entering the image forming unit than a point on the image forming unit conjugating to a near point on the virtual image plane.